Search Results (193)

As the range of applications for amphibious robots expands, higher demands are being placed on their working time and working range. This paper proposed a power supply system for an amphibious robot based on wave energy generation, which can convert wave energy into electric energy to enhance endurance. First, the no-load induced electromotive force, magnetic line distribution vector diagrams, and magnetic density cloud diagrams of the cylindrical and flat generators were compared by finite element simulation, which determined that the cylindrical structure has better power generation performance. Then, the electromagnetic parameters of the cylindrical generator were analyzed using Ansys Maxwell, and the final dimensions were determined. Finally, the wave motion was simulated using a swing motor, and the effects of different cutting speeds for the actuator before and after rectification, as well as series-parallel capacitance on the power generation performance of the designed generator, were experimentally analyzed. This provides a potential solution to enhance the working time and working range of amphibious robots. Full article

Double-suction centrifugal pumps are extensively employed in industrial applications owing to their high efficiency, low vibration, superior cavitation resistance, and operational durability. This study analyzes how impeller oblique cutting angles (0°, 6°, 9°, 12°) affect a double-suction pump at a fixed 4% trimming ratio and constant average post-trim diameter. Numerical simulations and tests reveal that under low-flow (0.7Q_d) and design-flow conditions, the flat-cut (0°) minimizes reflux ratio and maximizes efficiency by aligning blade outlet flow with the mainstream. Increasing oblique cutting angles disrupts this alignment, elevating reflux and reducing efficiency. Conversely, at high flow (1.3Q_d), the 12° bevel optimizes outlet flow, achieving peak efficiency. Pressure pulsation at the volute tongue (P11) peaks at the blade-passing frequency, with amplitudes significantly higher for 9°/12° bevels than for 0°/6°. The flat-cut suppresses wake vortices and static–rotor interaction, but oblique cutting angle choice critically influences shaft-frequency pulsation. Entropy analysis identifies the volute as the primary loss source. Larger oblique cutting angles intensify wall effects, increasing total entropy; pump chamber losses rise most sharply due to worsened outlet velocity non-uniformity and turbulent dissipation. The flat-cut yields minimal entropy at Q_d. These findings provide a basis for tailoring impeller trimming to specific operational requirements. Furthermore, the systematic analysis provides critical guidance for impeller trimming strategies in other double-suction pumps and pumps as turbines in micro hydropower plants. Full article

Curvilinear V-grooves are increasingly employed in functional surfaces with applications ranging from fluidics to tribology and optics. Despite their widespread use, the accurate and repeatable fabrication of curvilinear V-grooves remains challenging due to their inherent geometric complexity and the lack of relevant commercial CAD/CAM systems. To address this, the present study proposes a CAD/CAM integrated framework capable of automating the design and fabrication of functional surfaces comprising curvilinear V-grooves generated by multi-axis single-point diamond cutting (SPDC). The framework is organized into three main functional blocks supported by seven secondary modules that encompass the entire process from V-groove geometry definition to cutting. The developed framework was practically validated by fabricating sinusoidal V-grooves on a flat surface and testing the capillary flow functionality of a curvilinear pattern. These results demonstrate the relevance of the integrated framework to curvilinear V-groove fabrication, thereby offering a versatile solution for certain types of surface engineering applications. Full article

This paper presents the design and validation of a novel specialized fixture device for machining inclined planes with barrel cutters on 3-axis CNC machine tools. Barrel milling, also known as Parabolic Performance Cutting (PPC), is extensively used on 5-axis machines to enhance the efficiency of machining complex surfaces. While significant research has focused on optimizing barrel milling for aspects such as surface roughness and cutting forces, implementing this technique on 3-axis machines poses a challenge due to limitations in tool orientation. To overcome this, an innovative adaptable device was designed, enabling precise workpiece orientation relative to the barrel cutter. To overcome this limitation, an adaptable device was designed that enables precise workpiece orientation relative to the barrel cutter. The device utilizes interchangeable locating elements for different cutter programming angles (such as 18°, 20°, and 42.5°), thereby ensuring correct workpiece positioning. Rigid workpiece clamping is provided by the device’s mechanism to maintain precise workpiece positioning during machining, and probing surfaces are integrated into the device to facilitate the definition of the coordinate system necessary for CNC machine programming. Device control was performed using a Hexagon RA-7312 3D measuring arm. Inspection results indicated minimal dimensional deviations (e.g., surface flatness between 0.002 mm and 0.012 mm) and high angular accuracy (e.g., angular non-closure of 0.006°). The designed device enables the effective and precise use of barrel cutters on 3-axis CNC machines, offering a previously unavailable practical and economical solution for cutting tool tests and cutting regime studies. Full article

This paper proposes a method for determining the contact temperature in the secondary shear zone. The input data include the results of the experimental tests of the orthogonal turning of a Ti-6Al-4V titanium workpiece using uncoated WC-Co tools with a flat rake face. The cutting force components were recorded using a piezoelectric dynamometer, a thermovision camera was used to record the temperature in the cutting zone, and a high-speed camera was used to record the chip-forming process. The independent variables included machining parameters, feed rate, cutting speed, and rake angle. A dual-zone thermomechanical cutting process model that accounted for the sticking and sliding areas was adapted for the identification of the heat flux in the chip–rake face contact zone. Then, based on the Shaw approach, the partition coefficients were determined for the contact temperature on the chip–tool tip contact. In addition, the results of the experimental tests allowed the determination of the relationship among the process parameters, friction coefficients, and the length of the contact of the chip with the tool rake face. A graphical visualization of the temperature distribution on the tool rake face was performed using the MATLAB PDE 3.9 software package. Although the application of the dual-zone model has been well presented in the literature, the results provided in this paper may be helpful in analyzing and modeling thermal phenomena in the secondary shear zone. Full article

The increasing demand for precision-engineered machined components across diverse sectors highlights the importance of optimizing machining procedures. The improvement of milling strategies is significant in the production of flat surfaces and slots of different sizes. The choice between milling techniques can significantly impact the final product quality and production efficiency. This study provides a detailed examination of the relative effectiveness of plunge milling (axial feed) versus face milling (radial feed) techniques, concentrating on critical performance metrics such as cutting force and surface roughness. In our systematic approach, we varied key milling parameters (feed per tooth, depth of cut, and cutting speed). We conducted a series of experiments to quantify the resulting cutting forces and surface finish quality employed under different conditions. The analysis reveals notable performance differences between the two milling methods at various parameter settings. Through statistical and graphical analysis, we clarify the relationships between milling parameters and the resultant outputs, offering a deeper understanding of the factors influencing machining efficiency. The results reveal significant differences between plunge milling and face milling, with plunge milling exhibiting lower cutting forces, while face milling demonstrated superior surface quality. The insights granted from this research have implications for optimizing milling operations. Full article

The recovery of lithium from extracts obtained from a black mass of spent lithium-ion batteries treated with a ternary solvent system at acidic pH was investigated using flat-sheet nanofiltration (NF) membranes operated according to a dead-end configuration. Specifically, four samples obtained at different pH values (2.5 and 5) and extraction times (48, 96 and 168 h) were treated in selected operating conditions by using two commercial polymeric membranes (denoted DK and HL, with an approximate molecular weight cut-off of 150–300 Da) up to a volume reduction factor (VRF) of 4. Membrane performance was assessed in terms of productivity and selectivity towards specific ions, including lithium. For most treated samples, the HL membrane exhibited higher permeate fluxes in comparison to the DK membrane. However, the DK membrane performed better in terms of lithium rejection than the HL membrane, with a negative rejection at VRF 4 observed for all treated samples. More than 90% of multivalent ions were rejected by both membranes independently of the VRF. The membrane ability to retain multivalent ions led to their progressive concentration in the retentate as the VRF increased. The extraction time did not impact the NF performance of both membranes in terms of ion rejection. For the DK membrane conditions of extraction of 96 h and pH 5 represented the best trade-off between flux, ion rejection, and total lithium recovery. Full article

This article proposes a mathematical model for experimental estimation of the volumetric heat capacity and thermal conductivity of flat samples, in particular samples cut from potato tubers. The method involved using two pairs of samples, each of which includes the test sample and a reference sample. The pairs of samples were pre-cooled in a refrigerator to a temperature that was 10 to 15 °C below room temperature. Then, the samples were removed from the refrigerator and placed in an air thermostat at ambient temperature, with one pair of samples additionally blown with a weak air flow. Using a thermal imager, the surface temperatures of the samples were recorded. The temperature measurement results were processed using the proposed mathematical models. The temperature measurement results of the reference samples were used to determine the Bi numbers characterizing the heat exchange conditions on the surfaces of the test samples. Taking into account the found Bi values, the volumetric heat capacity and thermal conductivity were calculated using the formulas described in the article. The article also presents a diagram of the measuring device and a method for processing experimental data using the results of experiments as an example, where potato samples were used as the test samples, and polymethyl methacrylate samples were used as the reference samples. The studies were conducted at an ambient air temperature of 20 to 24 °C and at a Bi < 0.3. The specific heat capacity of the potato samples was in the range of 2120–3795 J/(kg·K), and the thermal conductivity was in the range of 0.17–0.5 W/(m·K) with a moisture content of 10–60%. Full article

The cutting length of milling tools must be longer than the axial distance of the material to be processed. In fact, in most cases, the cutting length far exceeds the thickness of the material to be removed. Therefore, along the entire length of the milling-tool flutes, only the area farthest from the shank wears out, leaving the rest of the tool practically without any wear, especially in the area closest to the shank. This research analyses a toolpath model to use the complete length of the milling tool flutes, in those machining operations in which it is possible, with the objective of reducing the costs associated with tool wearing and resharpening. This improves the tool performance, which clearly increases the sustainability of the milling process. For this purpose, it is necessary to transform the numerical control programme that performs a flat (2D) toolpath into a helical (3D) one by decomposing the arcs and rectilinear segments into a succession of points within a precision range. A negative aspect of this method is that it can only be applied to bottomless contours in processes of air-contour milling. Full article

Retina-like photoimaging devices with features such as a wide-field-of-view and high spatial resolution have wide application prospects in retinal prosthetics and remote sensing. However, the fabrication of flexible and conformal surfaces is hindered by the incompatible microfabrication processes of traditional rigid, silicon-based substrates. A kirigami strategy for hemispherical surface assembly is proposed to construct a MoS₂-based retina-like photodetector array. The device is first fabricated on a flat polyimide (PI) substrate and then tailored using a laser. By approximating the spherical surface using planar sectors, the laser-cut PI film can tightly adhere to the PDMS spherical shell without significant wrinkles. The responsivity and specific detectivity of our conformal photodetector can reach as high as 247.9 A/W and 6.16 × 10¹¹ Jones, respectively. The array integrates 180 pixels on a spherical crown with a radius of 11 mm, and a hollow letter “T” is successfully recognized. Comprehensive experimental results in this work reveal the utility of our device for photoelectric detection and imaging. We believe that our work provides a new methodology for the exploitation of 2D material-based retinal image sensors. Full article

This study aimed to evaluate the micro-tensile bond strength (µTBS) of two types of composites for indirect restoration, luted to enamel and dentin with self-adhesive cement. Moreover, it aimed to evaluate the impact of thermocycling on bond strength. Sixteen flat enamel and dentin surfaces of human molars were cemented to equal flat specimens of the laboratory composite Signum ceramis and the CAD/CAM block Cerasmart. Half of the specimens of the group underwent thermocycling. After that, the samples were cut into 80 beams for µTBS analysis. The data were analyzed using Levene’s test and the independent sample t-test. The micro-tensile bond strength tests revealed that thermocycling significantly reduced the adhesive bond. Dentin bonds better to conventional laboratory composites. Enamel bonds are better than composite blocks for milling. Full article

At present, the problems of the low cutting reliability and poor cutting quality of carrot harvesters in China are particularly prominent, directly leading to the problems of high root and stem damage rates, low stem and leaf cutting rates, and low cutting surface flatness rates. In order to solve these problems, we developed a disc-type double-disc cutting device. Based on the structural analysis and the central combination design theory of Box–Behnken, using three factors as influencing factors, namely, clamping and conveying speed, the rotary speed of the disc cutter, and the thickness of the disc cutter. A response surface experiment was carried out to analyze the influence of each factor on the high damage rates of the rhizome, the clean rates of stems and leaves, and the flatness rate of cutting surfaces to optimize the influencing factors. According to the test results, a regression mathematical model between test parameters and performance indexes was established, and optimization verification was carried out according to the regression model between test factors and indexes. Finally, the optimal parameter combination is as follows: a clamping and conveying speed of 1.0 m/s, a rotary speed of the disc cutter of 193.5 r/min, and a thickness of the disc cutter of 3.6 mm. The results of the field experiment showed that the root and stem damage rate was 2.61%, the stem and leaf-cutting rate was 87.32%, and the cutting surface flatness rate was 89.87%. Compared with a set of parameters commonly used in double-disc cutters to harvest carrots under the same conditions, the corresponding root and stem damage rates, stem and leaf-cutting rates, and productivity decreased by 2.16%, 1.97%, and 1.87%, respectively, and the comprehensive performance was obviously improved. The proposed research method can well simulate the cutting process in carrot harvesting and provide support for the development of carrot harvesting equipment. Full article

As a bionic flow control structure, leading-edge serrations have been proven to effectively suppress the aerodynamic noise of airfoils. Compared with single-wavelength serrations, a greater noise reduction potential can be obtained for airfoils with the double-wavelength serrations because of the phase interference at different tip-to-root ratios. In this study, in order to reduce the aerodynamic noise of a flat plate operating in a steady uniform flow, double-wavelength leading-edge serrations based on Ayton’s analytical model are optimized by the meta-heuristic optimization algorithm. The effects of different double-wavelength serrations on the noise characteristics of the flat plate are investigated. By comparing and analyzing the radiation integral function and quantifying the sound pressure along the leading edge of the flat plate, the local source cut-off effect resulting from the large transition curvature of the root and phase difference superposition is analyzed in detail. The results show that, before the first inflection point, the convex sinusoidal and iron-shaped serrations can significantly reduce the aerodynamic noise of the flat plate. When the concave ogee-shaped serrations are adopted, the reduction of the high-frequency noise is more obviously. Especially when the slits are embedded at the roots of the optimized leading-edge serrated structures, the improved design further promotes an additional noise reduction level of 0.7 dB for the flat plate. Through numerical studies, the coupled noise reduction mechanism of the serration roots and the slits is also revealed. Full article

This study examines the treatment of industrial wastewater generated during vibro-abrasive steel and Zn-Al alloy parts machining in a Polish metal-processing plant. The machining process uses grinding fluids, which are sent for disposal after becoming saturated with contaminants, incurring high costs. A two-stage filtration process was investigated: an initial bag filtration (pore size 5 µm) followed by a low-pressure (4 bar) ultrafiltration with polyacrylonitrile membranes (30 kDa cut-off). The studies were carried out on a laboratory scale in a cross-flow system using a batch configuration. The initial filtrate flux was 0.116 mL min⁻¹ cm⁻² and 0.050 mL min⁻¹ cm⁻² for Zn-Al alloy and the steel wastewater, respectively. Key physicochemical parameters, including turbidity, COD, and TOC, were analysed for raw wastewater, feed, retentate, and permeate. Significant reductions in contaminant concentrations were achieved, with comparable total efficiencies for both the wastewaters tested. The reductions in turbidity, COD, TOC, anionic surfactants, total phosphorus and non-ionic surfactants ranged from 80% to almost 100%. A complete removal of total suspended solids was achieved. The novelty of this research lies in applying polyacrylonitrile flat-sheet membranes to treat wastewater from vibratory machining of ferrous and non-ferrous materials and recycle reclaimed water, which has not been systematically explored in previous studies. The study demonstrates the potential of low-pressure membrane filtration for wastewater recycling, offering insights into environmentally friendly and energy-efficient management of industrial wastewater. Full article

The effectiveness of a machining process can be determined by analysing the quality of the generated surface and the rate of tool wear. Stellite is highly challenging to machine, which is why it is primarily processed through grinding methods. This study concentrates on the impact of cutting parameters and tool wear (VB_b, KB_b) on the created surface roughness surface (Rt, Ra, Rz) during the orthogonal cutting of Stellite 6, which is overlaid on a steel surface, C45, prepared by means of HP/HVOF (JP-5000). The results indicate that the dominant influence on the change in the total roughness profile height value (Rt) is the mutual interaction of cutting speed and depth of cut at 16% (p < 0.000). The greatest impact on the change in the mean arithmetic deviation of the roughness profile (Ra) value is the interaction of cutting speed, tool front angle, and depth of cut with a 15% share (p < 0.000), as well as on the change in the Rz value (15%) and tool wear VB_b (25%). This investigation lays the groundwork for potentially substituting the processing of flat surfaces with hardened layers created by thermal spraying (such as Stellite 6) with grinding or methods that offer greater efficiency from both economic and technological perspectives. Full article